"It might be in your pocket or purse or on a table - perhaps with the screen off. We want to make sure you see important Tweets even when you’re not looking at Twitter at the moment. To help with that, today we’re launching push notifications for @mentions".

Whenever someone you follow mentions you, you'll get notified. Notifications for @mentions will initially be available via SMS.

To turn on SMS notifications you need to fiddle with your Twitter settings on the main site.

In addition to the new @mentions function, Twitter is also planning to add push notifications for Messages to Twitter for iPhone, as well as "working hard" to get this feature onto Android and Windows Phone 7 as well.